Time-dependent CP asymmetries $B_s$ decays at LHCb

The LHCb experiment will search for New Physics in $b_s$ mixing. The $b_s$ mixing phase will be extracted from the measurement of the time-dependent CP asymmetry in exclusive $\mathrm{B}_s$ decays governed by the $b \rightarrow c\bar{c} s$ quark-level transition. Large New Physics effects can be discovered or excluded with the data collected during the very first physics run of LHC. Based on Monte Carlo simulations of the LHCb detector, the expected sensitivity with $2~\mathrm{fb}^{-1}$ on the CP-violation parameter $\phi_s$, is $\sigma(\phi_s) = 0.022$.